"What we teach and try to talk about is first thing you want the students to do is run. And upon my arrival and the arrival of the officers was we saw a chaotic scene outside with people running everywhere. So yes, the fire alarm being pulled probably assisted with evacuating the school and that was a good thing that was done," the chief said.

Finch told ABC News she also heard that yet another student helped subdue the assailant.

As many as 20 people were injured in the early morning stabbing spree at Franklin Regional High School, according to Westmoreland County emergency management spokesman Dan Stevens.

No fatalities were reported, though Stevens said at least four people suffered "serious" injuries.